AbstractIntroductionIt has been suggested that women with obesity have increased risk of developing placenta accreta spectrum (PAS). It is unclear if this is independent of the increased risk of cesarean delivery seen with obesity itself. The aim of this study was to explore the association between maternal obesity and PAS, particularly severe PAS (percreta).Material and methodsThis is a cohort study based on cases recorded in the International Society for Placenta Accreta Spectrum (IS‐PAS) database between April 2008 and May 2019. Multivariable logistic regression was used to explore the effect of maternal obesity on severity of PAS; this model was adjusted for other known risk factors including previous cesarean deliveries, maternal age, and placenta previa. The estimated rate of obesity in a hypothetical cohort with similar characteristics (previous cesarean delivery and same parity) was calculated and compared with the observed rate of obesity in the women of the PAS cohort (one sample test of proportions).ResultsOf the 386 included women with PAS, 227 (58.8%) had severe disease (percreta). In univariable analysis, maternal obesity initially appeared to be associated with increased odds of developing the most severe type of PAS, percreta (odds ratio [OR] 1.87; 95% CI 1.14‐3.09); however, this association was lost after adjustment for other risk factors including previous cesarean delivery (OR 1.44; 95% CI 0.85‐2.44). There was no difference in the observed rate of obesity and the rate estimated based on the risk of cesarean delivery from obesity alone (31.3% vs 36.8%, respectively; P = .07).ConclusionsObesity does not seem to be an independent risk factor for PAS or severity for PAS. These findings are relevant for clinicians to provide accurate counseling to women with obesity regarding increased risks related to pregnancy.